1. Technical Field
The present invention belongs to a technical field for improving a polarizing plate in terms of wide viewing angle characteristics, and specifically relates to a wide viewing angle polarizing plate and a liquid crystal display device using the same.
2. Background Art
In a transmission liquid crystal display device, in general, a pair of polarizing plates is used and disposed so that their polarization axes are orthogonal to each other. However, even when the two polarizing plates are superimposed in such a manner that a crossing angle of the polarization axes is orthogonal, the resulting liquid crystal display device is deviated from orthogonality against incident light from the oblique direction. This is a factor of causing light leakage in the oblique direction in the black state. Accordingly, for the purpose of providing a liquid crystal display device with excellent viewing angle characteristics, it is important to reduce the viewing angle dependency of a polarizing plate. As a wide viewing angle polarizing plate, there have hitherto been made various proposals to combine a polarizer with a retardation layer exhibiting prescribed optical characteristics (see JP-A-2001-350022). Also, it has also been proposed to utilize a polarizer whose refractive index in the transmission axis direction falls within a prescribed range (see JP-A-10-268294).
Also, there is proposed a dichroic polarizer in which absorption anisotropy and refractive index anisotropy are satisfied with a prescribed relation (see JP-T-2003-524207).
Also, there is proposed a polarizing plate having a polarizing layer, including a region where a dichromatic function unit (i.e. dichromatic dye) is subjected to orientation control by having an angle of inclination with a polarizing plate surface. (see JP-A-2007-233162).